public function generateManifest() {
        $file = new Gpf_Io_File(Gpf_Paths::getInstance()->getAccountConfigDirectoryPath() . self::getManifestFileName());
        $file->setFileMode('w');
        $file->open('w');

        if ($file->isOpened()) {
            $file->write('{"betaManifestVersion":1,"version":"' .
            Gpf_Application::getInstance()->getCode() . '_' .
            Gpf_Application::getInstance()->getInstalledVersion() . md5(rand()) .
            '","entries":[{"url":""}');

            //add js libraries
            $this->addJsLibraries($file);

            //add images, css and other theme resources
            $this->addImages($file);

            $file->write(']}');
            $file->close();
        }
    }